A recent development in semiconductor memory devices involves spin electronics, which combines semiconductor technology and magnetics. The spin of electrons, rather than the charge, is used to indicate the presence of a “1” or “0.” One such spin electronic device is a magnetic random access memory (MRAM) device which includes conductive lines (wordlines and bitlines) positioned in a different direction, e.g., perpendicular to one another in different metal layers, the conductive lines sandwiching a magnetic stack or magnetic tunnel junction (MTJ), which functions as a magnetic memory cell. A current flowing through one of the conductive lines generates a magnetic field around the conductive line and orients the magnetic polarity into a certain direction along the wire or conductive line. A current flowing through the other conductive line induces the magnetic field and can partially turn the magnetic polarity, also. Digital information, represented as a “0” or “1,” is storable in the alignment of magnetic moments. The resistance of the magnetic memory cell depends on the moment's alignment. The stored state is read from the magnetic memory cell by detecting the component's resistive state.
An advantage of MRAM devices compared to traditional semiconductor memory devices such as dynamic random access memory (DRAM) devices is that MRAM devices are non-volatile. For example, a personal computer (PC) utilizing MRAM devices would not have a long “boot-up” time as with conventional PCs that utilize DRAM devices. Also, an MRAM device does not need to be powered up and has the capability of “remembering” the stored data. Therefore, it is expected that MRAM devices will replace flash memory, DRAM and static random access memory devices (SRAM) devices in electronic applications where a memory device is needed.
Because MRAM devices operate differently than traditional memory devices, they introduce design and manufacturing challenges. For example, the magnetic material layers and other metal layers that form the magnetic memory cells of an MRAM device are difficult to etch and have a high sputter component, resulting in re-deposition of conductive material in undesired locations.